Circuit arrangement for the radio interference suppression in brightness control devices using the phase gating principle

ABSTRACT

Circuit arrangement using carrier frequency control voltage on low voltage power lines for radio interference suppression in brightness control devices using the phase gating principle, comprising a radio frequency interference filter including an interference suppression choke coil and wherein a semiconductor switch combined with the interference suppression choke coil is connected in series with the load circuit which includes at least one incandescent lamp and wherein a capacitor is shunted in parallel with the series-connection of the interference suppression choke and the semiconductor component, including a further choke in the load circuit which presents a high impedance to the carrier-frequency control voltage, thereby preventing the loading of the control voltage on the power lines caused by the low impedance of the capacitor at the carrier frequency when the semiconductor component is in the non-conducting state.

The invention relates to a circuit arrangement for the radiointerference suppression in brightness control devices for incondescentlamps according to the phase gating principle, wherein a semiconductorswitch is connected in series with an interference suppression choke andthe load circuit, and having a capacitor shunted across thesemiconductor switch and the interference suppression choke.

The known brightness control devices of this general type, which can beoperated manually, have a disconnect switch, by which the circuitarrangement can be separated from the power line.

Brightness control devices which are designed as remote-controlledswitches and are switched remotely by means of a high frequencytransmitter, using low-voltage lines for transmitting transmittingfrequencies are on the other hand continuously connected to the line. Inthe latter case, the radio interference suppression components of thesebrightness control devices, consisting of a choke and a capacitor, arecontinuously connected to the line, and due to the resistance ofincandescent bulbs which have low resistance in the "off" condition, thetransmitting voltage is heavily attenuated by the capacitor.

Thereby, the number of brightness control devices which can maximally beconnected within a remote-control system is greatly limited. Within sucha system, the a transmitter which can operate, for instance, 256switching points, at most 16 brightness control devices can therefore beconnected. In many cases, however, a larger number of brightness controldevices must be able to be connected. Since the transmitter voltagewithin a system must not fall below the response threshold, thearrangement of brightness control devices is limited due to thedescribed conditions.

In order to overcome this problem, it has been attempted to design theradio interference suppression circuit in such a way that a capacitor isused which has substantially less capacitance, for instance, only about30% of that customary capacitance, but using instead a radiointerference suppression choke with more coil turns. The suppressioncircuit values that were required were obtained thereby, but the radiointerference suppression choke was made more expensive due to both thelarger number of turns and the additional material required as well asthe increased manufacturing costs. In addition, a problem of greatertemperature rise in the coil arose, so that the overall size of theentire circuit was adversely affected thereby.

Finally, by this measure it was not achieved to operate a number greaterthan maximally 16 brightness control devices within a system.

It is an object of the invention to increase the number of remotelycontrollable brightness control devices in a remote-controlled systemwith carrier-frequency utilization of low-voltage lines without heavilyloading the high-frequency transmitting voltage.

According to the invention, the problem is solved by the provision thatthe attenuation of the radio interference suppression components, iscancelled in devices using high-frequency utilization of low-voltagelines, if the semiconductor switch does not conduct, by arranging afurther choke in the load circuit. Because of this arrangement, theseries circuit of choke and capacitor becomes high-impedance in the"off" condition. Thus, the heavy loading of the high-frequencytransmitting voltage, on the low-voltage line is cancelled.

The invention further includes a ferrite core with only few coil turnsas the further choke. Due to the fact that the ferrite core has theeffect of quickly saturating the choke when current flows, it isachieved that the further choke loses its detrimental effect on theradio interference suppression circuit when the remote-controlledbrightness control device is switched on, and thereby, effective radiointerference suppression is achieved in the switched-on condition.

The circuit arrangement according to the invention is shown in thedrawing in several embodiment examples, where

FIG. 1 shows a schematic circuit diagram, of the arrangement,

FIG. 2 shows the construction of a remotely controlled brightnesscontrol device for under-plaster installation, seen partly in crosssection, and

FIG. 3 shows a remotely controlled brightness control device in anadd-on construction as a plug-in module.

It can be seen in the circuit diagram according to FIG. 1 that theremote controlled brightness control device can be connected to alow-voltage line network by the terminals L and N. The brightnesscontrol device consists of components well known for devices of thistype such as a triac T, used as the semiconductor switch which obtainsits firing pulses from the control S in accordance with the setting ofthis control.

The interference suppression choke Dr1 and the capacitor C serve forradio interference suppression in a manner which is known. The consumeris V, which may be an incandescent lamp or another controllableapparatus, such as a motor for instance. According to the invention, thefurther choke Dr2 is arranged in series with the capacitor C in the loadcircuit. This further choke Dr2 consists of a ferrite core with only afew coil turns wound thereon. In this way, the further choke Dr2requires only a very small volume.

As may be seen from FIG. 2, this further choke Dr2 can be arranged, inthe construction of the brightness control device especially forconcealed installation, within the winding window of the interferencesuppression choke Dr1. This brightness control device for concealedinstallation consists of a two-part housing, namely, an upper housingpart 1 and a lower housing part 2, between which a circuit board 3 withthe other electronic components, on which for instance the triac T andthe elements of the control device S is mounted. Underneath the circuitboard 3 within the lower housing part 2, the interference suppressionchoke Dr1 and the further choke Dr2 are mounted. The brightness controldevice can be fastened in an under-plaster box 4 in a known manner bymeans of spreading tabs 5. It is covered by a cover plate 6 toward theoutside.

In the presentation according to FIG. 3, the brightness control deviceis mounted with its electronic components, including its selectingswitches provided for the remote selection of the equipment and theselection of the code for remote operation which is not part of theinstant invention and is therefore not shown, in a housing 10, to whicha connector part with the jacks 11 and a protective contact bracket 12is added. As can be seen from the connector part, shown open, thefurther choke Dr2 is installed here in an empty space of the connectorpart and can be attached there by suitable accommodations in thehousing. The electrical connection of the coil winding of this furtherchoke Dr2 can be performed in a very simple manner between the jack 11and the one input line 13 of the brightness control device.

I claim:
 1. Circuit arrangement using carrier frequency control voltageon low voltage power lines for radio interference suppression inbrightness control devices using the phase gating principle, comprisinga radio frequency interference filter including an interferencesuppression choke coil and wherein a semiconductor switch combined withthe interference suppression choke coil is connected in series with theload circuit which includes at least one incandescent lamp and wherein acapacitor is shunted in parallel with the series-connection of theinterference suppression choke and the semiconductor component,including a further choke in the load circuit which presents a highimpedance to the carrier-frequency control voltage, thereby preventingthe loading of the control voltage on the power lines caused by the lowimpedance of said capacitor at the carrier frequency when thesemiconductor component is in the non-conducting state.
 2. Circuitarrangement according to claim 1, comprising a ferrite core with only afew coil turns as the further choke.